The present invention relates to a contact switch and particularly to a contact switch adopted for use in electronic products such as mouse to form electric connection by depressing a pushbutton.
Contact switches or microswitches have been widely used in electronic products. In order to confine Electro-Static Discharge (ESD) and avoid electrical failure, to lower the conductive position of metal contact legs to prevent instantaneous high voltage discharge from occurring and affecting the inner circuits has become one of the key focuses of research and development efforts in the switch industry.
Refer to FIGS. 1A and 1B for U.S. Pat. No. 5,432,311, entitled: xe2x80x9cCommon conducting unit for a contact switchxe2x80x9d granted to Applicant. For the contact switch adopted for two staged electronic products, it has a smaller total size when coupled with the mating device. Thus it is desirable for small size products such as mouse. However, as ESD test standards have become increasingly strict, industry requirement of the test standard for non-contact electronic products is +/xe2x88x9216 KV. It is twice the normal test standard. Hence industry requirements for ESD test also are higher. The prior art has a common leg formed in U-shape. Installation point of the micro mechanism is located on a upper portion closed to the depressing opening. It cannot meet the stricter test requirements. Hence to lower installation for the micro mechanism is a big issue to be overcome.
U.S. Pat. No. 5,171,945, entitled: xe2x80x9cContact switchxe2x80x9d which also was granted to the Applicant, discloses a contact switch which has a mounting plate member that enables a micro mechanism to be installed on a common leg spacing from a depressing opening at a greater interval. But it is mainly adopted on electronic switches of three conductors. The design has to couple with other connection legs and casing. If the structure of the common leg can be adapted on existing switches, it would be a great breakthrough.
Moreover, the pushbutton employed in the foregoing switches has a drawback. When the pushbutton is depressed into the casing to push the spring, it is supported only by the spring. A skew is prone to take place and results in a non-vertical downward pressure. The spring tends to receive a uneven or inadequate force and result in electric connection failure. The skewed downward pressure could even cause deformation and damage of the spring. This is another issue to be resolved.
The primary object of the invention is to resolve the aforesaid disadvantages. The inventions provides an improved contact switch structure that combines the advantages of the two patents mentioned above and couples with matching casing, lid and legs. The casing has a housing compartment which has a first and a second anchor ledges projecting in the same direction of the depressing opening of a first contact leg. The micros mechanism installation location is lowered to achieve a higher ESD. In addition, the depressing opening of the casing is extended to form a retaining section which forms a depressing space with a first anchor flange resulting from the micro mechanism being located at a lower position, the pushbutton may be moved in the depressing space without skewing. Thus the contact switch can establish desired electric connection when depressed.